1. Field of the Invention
The present invention relates generally to sheet feed devices which comprise a first tray and a second tray positioned on the first tray, and are configured to increase the capacity of the first tray without increasing the height of the sheet feed device, and to image recording apparatus which comprise, such a sheet feed device.
2. Description of Related Art
A known sheet feed device, such as the sheet feed device described in Japanese Laid-Open Patent Application Publication No. 2007-223786, is used in a known image recording apparatus, such as a printer or a facsimile device, or both. The known sheet feed device includes a first tray for storing a plurality of sheets having a first size, and a second tray for storing at least one sheet having a second size which is smaller than the first size. The second tray, which is thinner than the first tray, is positioned on the first tray, such that the second tray is selectively advanced or retracted with respect to a sheet feed direction. When the second tray is retracted upstream in the sheet feed direction, a feed roller applies a force on the sheets in the first tray. The feed roller cooperates with a separation member positioned at a downstream end of the first tray to separate and feed an uppermost sheet to a recording unit via a U-shaped path. When the second tray is advanced downstream in the sheet feed direction, the feed roller applies a force on the sheets in the second tray.
The second tray is supported on its opposed sides, which extend in the sheet feed direction, by rails formed on upper surfaces of opposed side plates of the first tray, such that the second tray may slide on the first tray. When the feed roller feeds the sheets from the second tray, a downstream end of the second tray is supported by the separation member.
The feed roller is positioned at a free end of an arm, and a base end of the arm is pivotably attached to a drive shaft. As an angle of inclination of the arm with respect to an upper surface of the sheets decreases, a contact force applied by the feed roller on the sheets decreases, such that a sheet drawing force associated with the feed roller also decrease, which may result in an idle rotation of the feed roller, i e., a failure to feed a sheet. The angle of inclination of the arm is formed between an upper surface of the sheets and a line which connects a point at which the feed roller contacts the upper surface of the sheets and the pivot center of the arm.
In order to increase the maximum number of sheets which may be stored in the first tray, the height of the first tray may be increased. For example, the height of the first tray may be increased by about 5 mm in order to increase the capacity of the first tray from 100 sheets to 150 sheets. In this case, if the diameter of the feed roller, the length of the arm, the mounting height of the drive shaft, and the mounting height of the first tray are not altered, the angle of the arm with respect to the upper surface of the sheets on the second tray decreases.
In order to prevent a sheet feeding failure from the second tray, the mounting position of the feed unit including the arm and the feed roller may be raised, resulting in an increase in the height of the image recording apparatus. Thus, increasing the capacity of the first tray also may require modifying parts of the image recording apparatus other than the first tray and the second tray, e., may require modifying parts which have a relatively small height.